This research will seek to gain understanding of the interactions between genetic and nutritional factors in the development of mammals, and of the influence of nutritional factors on the teratogenicity of drugs. Specific objectives are to characterize the interaction between the mutant gene pallid and the essential trace element manganese, to investigate and establish other interactions between mutant genes or inbred strains of mice with trace elements, and to determine the influence of nutritional factors on drug effects during prenatal development. Biochemical, histological, and ultrastructural studies will be undertaken of mouse mutants and inbred strains, under various nutritional conditions.